1. Field of the Invention
The present disclosure generally relates to seat belt retraction devices, and more particularly, to a seat belt retractor having a tensioning mechanism that utilizes active material actuation to modify the tension in the belt.
2. Discussion of Prior Art
Seat belts and seat belt retraction mechanisms are known in the art, particularly with respect to automotive application. These mechanisms typically rely upon mechanical, electromechanical, or pneumatic means for storing energy and tensioning the belt once applied as a restraint. Concernedly, however, these mechanisms typically provide a constant magnitude of tension within the belt, regardless of current events or design preference.
During a crash event, for example, conventional retractors result in the transmission of peak forces to the occupant. In this regard, FIG. 1 presents an exemplary load versus payout (i.e., rate of dispensing belt webbing) graph of the forces that can be imparted on an occupant wearing a seat belt equipped with a standard retractor. As a result, load limiting retractors have been developed to limit the achievable peak force. Concernedly, however, these retractors also present various concerns in the art. For example, and as shown in FIG. 2, once triggered, conventional load limiting devices produce a constant limited load, and often employ complex electromechanical actuators subject to increased operational, energy consumption, and repair/maintenance costs.